Boiling roasting method for processing gold arsenic ore abroad (1)

Gold ore, gold-bearing sand ore and polymetallic ore (gold as a valuable component with collateral recovery) are the main sources of gold production.

Among the capitalist countries in the world, 85% of the gold reserves that have been identified are from gold ore and gold-bearing sands, and the remaining 15% are from non-ferrous metal composite ores, and the proportion of gold ore in the total metal balance is constantly increasing. increase.

Gold or the free state, or sulfide (mainly with pyrite) closely associated and various compounds present in solid solution. In some ores, gold is mainly present in various compounds and solid solution states. Therefore, it cannot be recovered by conventional cyanidation. This type of ore is considered to be an intractable ore.

The main gold producers in the capitalist world are South Africa, Canada and the United States. Gold production in these countries accounts for 86% of total gold production in industrial and developing countries . In 1874 , South Africa's gold production was 780 tons, accounting for 78% of the capitalist world's total gold production , Canada's 60 tons, accounting for 5% , and the United States 35 tons, accounting for about 3% . South Africa's gold mining industry is built on the basis of relatively simple, large-scale mining and production where ore is easier to process.

The obvious feature of the Canadian gold mining industry is that there are many small deposits. The composition of the ore in these deposits is very different, some of which are refractory gold-bearing ores. Different processes are used to recover gold for these difficult-to-treat ores. Because small-scale gold vein deposits, the mining and beneficiation plant equipment specifications small, labor productivity is low.

In the gold mining industry in the United States, gold is mainly recovered when dealing with non-ferrous metal ore (this part of the gold production accounts for about 40% of the total US gold production ). There are many gold deposits in the United States that are also like Canada - like tough ore.

A large number of scientific research work and production practices have proved that it is technically and economically reasonable to carry out oxidative roasting of refractory gold-bearing ores and concentrates and to prepare oxidative roasting as ore before cyanidation. The gold-containing materials that are difficult to handle are: copper products, arsenic products, and pyrite concentrates containing fine-grained gold. If cyanidation of these materials is carried out directly without calcination, the recovery of gold does not exceed 60 to 70% .

The results show that after the oxidative calcination, the refractory gold-containing material can obtain the porous calcine containing a large amount of fine grain exposure gold. In this way, the cyanide solution can enter the interior of the golden fruit, making the process of recovering gold easier. After pre-oxidation roasting and then treating the ore with cyanidation, the gold recovery can be increased to 95~97.5% .

Oxidative roasting of refractory gold - containing arsenic materials is quite complicated. Arsenic and sulfur must be removed during the roasting process. In order to remove arsenic, it needs to be in a weak oxidizing atmosphere and at a lower temperature ( 450~ 500 °C Under the conditions, arsenic is changed to arsenic trioxide and is excluded, or in a reducing atmosphere and high temperature ( 760 ~ 800 °C Under the conditions, arsenic is changed to arsenic trisulfide. At a temperature of 750~ 850 °C With a large excess of air, the sulfur in the sulfide is burned out at a suitable rate (ie, desulfurized) to minimize the amount of sulfate produced. Therefore, it is reasonable to use two-stage roasting to treat these gold-containing materials. In the first paragraph is mainly excluded during firing arsenic, sulfur second stage calcination is excluded. However, in some cases, for various reasons it may also be employed for a period of firing.

Gold - arsenic materials were - segment roasting method is Canada's first "Doyle" in 1946 the company began to use the concentrator. They are containing Au 200 grams / ton, S15% , As 5% of the arsenic pyrite concentrate slurry was calcined. The solids content in the pulp is 80% . The Liyu spray gun feeder directly feeds the slurry into the boiling layer of the roaster. The baking furnace is cylindrical and high 5.4 meters , the inner diameter is 2.64 meters . The diameter of the furnace in the boiling zone is reduced to 2.04 meters This is because the furnace has a refractory brick lining. At the top of the furnace, refractory bricks are built in the flue and cylinder. The bottom of the furnace is a steel plate lined with refractory cement. The steel plate has 120 disc-shaped holes and a corundum ball with a diameter of 6 mm. These corundum balls act as distribution valves and retaining devices when air is fed in to prevent the sand from falling into the furnace.

The height of the boiling layer is 1525 mm. When the air supply is stopped, the height is reduced to 1200 mm. The baking temperature is 640~ 650 °C . The temperature inside the furnace is adjusted by a water sprayer. Increasing the calcination temperature is highly undesirable because in this case the material is melted, which reduces the gold recovery of the calcine during the leaching process. During the roasting process, about - half (which contains 57% of the total gold ) roasting is discharged through the furnace door. Calcine about 40% (37% where gold) trapped a first inner cylinder. The remaining calcine (containing 6% gold ) was trapped in the second cylinder.

According to the data in the reference, the roaster has not been operated for 14 years.   repair. Firebrick bottom substrate repaired only once. Later, due to the improvement of the grade of talc in the concentrate and the formation of the furnace bottom (furnace knot) at the bottom of the furnace, it was stopped. Later, the position of the gun feeder was changed to the upper part of the furnace top, and the slurry was fed into the furnace in a fan-shaped line. Thus the slurry can be evenly distributed on the surface of the boiling layer. With this method of adding concentrate, most of the water can be removed when the concentrate falls. Changing the installation position of the gun feeder can also avoid the phenomenon of stopping the furnace due to the destruction of the boiling layer.

This has happened during the use of this type of roaster, namely in concentrates.   In the form of stibnite and antimony state have an adverse effect on the recovery of gold, especially when the antimony grade of more than 0.5%, this adverse effect is more obvious. In this case, molten metal particles may occur and is difficult to generate a layer on the surface thereof cyanide; film dissolution. This results in a significant reduction in gold recovery.

    CKoxHHoyp B aulahc ) After the boiling of the concentrator, the gold recovery rate in the cyanidation process is greatly improved.

The ore processing capacity of the Canadian concentrator is 500 tons / day and night. In 1951 a boiling roaster production. The treated concentrate contains Au 76 grams / ton; S18.8% ; As11.04% ; Sb 0.42% and Fe27.8% .

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